This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Our goal is to investigate a new strategy for female contraception that utilizes a novel class of drugs, the Selective Estrogen Receptor Modulators (SERMs). SERMs are compounds that selectively regulate estrogen action in various tissues. Estrogen is required for normal function of the reproductive tract, including transport of spermatozoa to the site of fertilization and capture of the oocyte by the fallopian tube after ovulation. Our study has 3 aims. Aim 1 is to examine whether therapy with an antiestrogenic SERM (ZK-SERM;Bayer-Schering Pharma) will disrupt/alter gamete transport and hence fertilization in rhesus macaques. Aim 2 is to determine if SERM therapy will block fertility in macaques during a contraceptive trial through the ONPRC Nonhuman Primate Contraceptive Core. Aim 3 will further assess the reversibility and long-term safety of ZK-SERM therapy for contraception. These studies could provide a prototype contraceptive for women that acts selectively at the level of the reproductive tract to prevent egg-sperm interaction and hence fertility.